Medical device employing liquid crystal block copolymers and method of making the same

ABSTRACT

A medical device, at least a portion of which is formed from a polymer composition including at least one liquid crystal block copolymer having at least one A block and at least one B block wherein the A block is formed of mesogenic repeat units and the B block is a soft block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/706,463 filed Feb. 16, 2010, which is a continuation of U.S. patentapplication Ser. No. 11/353,606 filed Feb. 14, 2006, issued as U.S. Pat.No. 7,662,129 on Feb. 16, 2010 which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to the field of insertable and/orimplantable medical devices, particularly to balloon catheter assembliesand components thereof.

BACKGROUND OF THE INVENTION

It is known to use liquid crystal polymers (LCPs) in combination withthermoplastic polymers, i.e. matrix polymers, for use in the manufactureof insertable and/or implantable medical devices such as catheterassemblies and components thereof such as inflatable medical balloonswhich can be disposed at the distal end of a balloon catheter assembly.For example, see commonly assigned U.S. Pat. Nos. 6,977,103, 6,905,743,6,730,377 and 6,284,333. See also U.S. Pat. Nos. 6,596,219, 6,443,925and 6,325,780 to Schaible.

Liquid crystal polymers are known to phase separate from commonly usedthermoplastic polymers into multiphase polymer compositions. Forexample, see U.S. Pat. Nos. 5,248,305 and 5,156,785 to Zdrahala.

Compatibilized blends of LCP and thermoplastic polymers have been foundsuitable for use as medical device balloon materials. See for examplecommonly assigned U.S. Pat. No. 6,242,063.

It would be desirable to have a liquid crystal polymer material or blendusing a liquid crystal polymer material which has increasedcompatibility over other previous LCP/polymer blends which could beemployed in the formation of medical devices, particularly in themanufacture of catheter assemblies or components thereof.

The art referred to and/or described above is not intended to constitutean admission that any patent, publication or other information referredto herein is “prior art” with respect to this invention. In addition,this section should not be construed to mean that a search has been madeor that no other pertinent information as defined in 37 C.F.R. §1.56(a)exists.

All US patents and applications and all other published documentsmentioned anywhere in this application are incorporated herein byreference in their entirety.

Without limiting the scope of the invention a brief summary of some ofthe claimed embodiments of the invention is set forth below. Additionaldetails of the summarized embodiments of the invention and/or additionalembodiments of the invention may be found in the Detailed Description ofthe Invention below.

A brief abstract of the technical disclosure in the specification isprovided as well only for the purposes of complying with 37 C.F.R. 1.72.The abstract is not intended to be used for interpreting the scope ofthe claims.

SUMMARY OF THE INVENTION

The present invention relates to polymer compositions useful in theformation of medical devices which include at least one liquid crystalblock copolymer having at least one A block and at least one B block.

The A block, which may also be referred to herein as the mesogenic(liquid crystal) block, may include any suitable mesogenic repeat(monomer) unit. As used herein, the term “mesogenic” shall be used torefer to those repeat units which impart liquid crystal properties, suchas stiffness and restriction to rotation, to the polymer. The term“mesogenic unit” as employed herein, shall be used to refer to anymonomer having a mesogen, as well as those monomers including spacerssuch as methylene groups, therein.

Any suitable mesogenic repeat unit may be employed herein. Suitably, theA block has at least one aromatic group per each mesogenic repeat unitand more suitably the A block has at least two aromatic groups per eachmesogenic repeat unit.

The B block is the soft block. Suitably, the B block is aliphatic.Suitably the B block has less than 10% aromaticity by weight of the Bblock, more suitably less than 5% aromaticity by weight of the B blockand most suitably substantially no aromaticity.

The polymers may be formed using conventional reaction techniques suchas condensation reactions as will be described in more detail below.

These polymers may be employed alone, or in combination with otherpolymers.

The polymers find particular utility in the formation of medical devicessuch as catheter assemblies and components thereof, including, forexample, shafts, tips, manifolds and balloons.

These and other aspects, embodiments and advantages of the presentinvention will become immediately apparent to those of ordinary skill inthe art upon review of the Detailed Description and Claims to follow.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific embodiments of the invention. Thisdescription is an exemplification of the principles of the invention andis not intended to limit the invention to the particular embodimentsillustrated.

All published documents, including all US patent documents, mentionedanywhere in this application are hereby expressly incorporated herein byreference in their entirety. Any copending patent applications,mentioned anywhere in this application are also hereby expresslyincorporated herein by reference in their entirety.

The present invention relates to polymer compositions useful in theformation of medical devices or at least a portion of a medical device.The polymer compositions include at least one liquid crystal blockcopolymer having at least one A block and at least one B block.

The A block is formed from mesogenic (liquid crystal) repeat units. Asemployed herein, the term “mesogenic” shall be used to refer to thoserepeat units (monomers) which impart liquid crystal properties to thepolymer. The mesogenic repeat unit may include a mesogen, as well as anyspacers such as methylene groups. Liquid crystal polymers have a thirdphase of matter which exists between a crystalline (solid) and anisotropic (liquid) phase, that has properties between those of aconventional liquid, and those of a solid crystal. For instance, aliquid crystal (LC) may flow like a liquid, but have the molecules inthe liquid arranged and oriented in a crystal-like way. It is themesogen of the mesogenic repeat unit which induces the structural order,rigidity and necessary restriction on movement that allows the polymerto display these liquid crystal properties. The mesogen is typicallymade up of one or more aromatic rings. Suitably, each mesogenic repeatunit has at least one aromatic group per each repeat unit, and moresuitably each mesogenic repeat unit has at least two aromatic groups pereach repeat unit.

The B block is the soft block of the liquid crystal block copolymer.Suitably, the B block is aliphatic. Suitably, the B block has less than10% aromaticity by weight of the B block, more suitably the B block hasless than 5% aromaticity by weight of the B block, and most suitably theB block has substantially no aromaticity.

The block copolymers may be of the general formula A-B diblock,(A-B)_(n) wherein n is 3 to 20, B-(A-B)_(n)-B wherein n is 3 to 20,A-B-A triblock, B-A-B triblock having soft segments at the free chainend, A-B-A-B-A pentablock, multiblock polymers such as A-B-C or A-C-Btriblock, B-(A-B-C)_(n)-B wherein n is 3 to 20, random block copolymers,etc.

The above list is intended for illustrative purposes only, and not as alimitation on the scope of the present invention.

The A block, which may also be referred to herein as the mesogenicblock, may include any suitable mesogenic repeat unit. Suitably, themesogenic repeat unit has at least one aromatic group per unit, and moresuitably the mesogenic repeat unit has at least two aromatic groups perunit. The A block of the liquid crystal block copolymer is characterizedby mesogenic repeat units which can provide the liquid crystal blockcopolymer with stiffness resulting from restriction on rotation causedby steric hindrance and resonance. For example, aromatic ring(s) canprovide both steric hindrance and resonance. Some mesogenic repeat unitsmay include both aromatic and aliphatic rings.

The A block may contain any number of repeating units up to about 50.

Suitably, the mesogenic block has an axial ratio, defined by the lengthof the molecule divided by the diameter (x=L/d), of at least three. Thisaxial ratio provides the mesogenic block with rod-like characteristics.

A variety of suitable mesogenic repeat units find utility in theformation of the A block of the liquid crystal block copolymer.

Classes of aromatic structural groups useful in the formation of eachmesogenic repeat unit include, but are not limited to, aromaticdicarboxylic acids, aromatic hydroxycarboxylic acids, aromaticaminocarboxylic acids, diphenols, and aminophenols, for example.

Examples of useful aromatic dicarboxylic acids include, but are notlimited to, 1,4-naphthalenedicarboxylic acid,1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid,biphenyl-4,4′-dicarboxylic acid, biphenyl-3,3′-dicarboxylic acid,diphenoxyethane-4,4′-dicarboxylic acid, diphenyl ether-4,4′-dicarboxylicacid, methylterephthalic acid, methoxyterephthalic acid,chloroterephthalic acid, 4-chloronaphthalene-2,7-dicarboxylic acid,1,3-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid,1,7-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid,biphenyl-3,4′-dicarboxylic acid, diphenyl ether-3,4′-dicarboxylic acid,4-methylisophthalic acid, 5-methylisophthalic acid, diphenylether-4,4′-dichloro-3,3′-dicarboxylic acid and iso- and terephthalicacid.

Examples of useful aromatic hydroxycarboxylic acids include, but are notlimited to, 4-hydroxy-3-methylbenzoic acid, 4-hydroxy-3-phenyl-benzoicacid, 4-hydroxy-2-ethylbenzoic acid, 3-chloro-4-hydroxy-benzoic acid,4-hydroxy-3-methoxybenzoic acid, hydroxyl benzoic acid including4-hydroxybenzoic acid and 3-hydroxybenzoic acid, hydroxynaphthoic acidincluding 6-hydroxy-2-naphthoic acid, etc.

Examples of useful diphenols include, but are not limited to,hydroquinone, t-butylhydroquinone, bromohydroquinone,chlorohydroquinone, methylhydroquinone, ethylhydroquinone,phenylhydroquinone, 4,4′-dihydroxydiphenyl, 4,4′-dihydroxydiphenylether, 4,4′-dihydroxydiphenylethane, 4,4′-dihydroxydiphenoxyethane,3,5′-dihydroxydiphenyl, 4-hydroxy-4′-carboxydiphenyl,3,5′-dihydroxydiphenyl ether, naphthalene, dihydroxynaphthaleneincluding 1,4-, 1,5- and 2,6-dihydroxynaphthalene, for example,4-methoxy-2,6-dihydroxynaphthalene, 1,3-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,2,7-dihydroxynaphthalene, 2,5-dichloro-1,6-dihydroxynaphthalene,4-methoxy-2,7-dihydroxynaphthalene,2,2′-dimethyl-4,4′-dihydroxydiphenyl,3,3′,5,5′-tetramethyl-4,4′-dihydroxydiphenyl,3,5′-dimethoxy-4,4′-dihydroxydiphenyl ether,1,2-(2-chloro-4-hydroxyphenoxy)-ethane resorcinol,3,4′-dihydroxydiphenyl, 3,4′-dihydroxydiphenyl ether,3,4′-dihydroxydiphenoxyethane, 4-chlororesorcinol, 4-bromoresorcinol,4-methylresorcinol, 4-phenylresorcinol, 4-ethoxyresorcinol, etc.

Examples of aromatic aminocarboxylic acids include, but are not limitedto, 2-aminobenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid,4-chloroanthranilic acid, 5-chloroanthranilic acid,3-amino-4-chlorobenzoic acid, 4-amino-3-phenyl-benzoic acid,4-amino-3-methoxybenzoic acid, 4-amino-3-phenoxybenzoic acid,6-amino-5-chloro-2-naphthoic acid, 6-amino-5-methyl-2-naphthoic acid and6-amino-5-methoxy-2-naphthoic acid, etc.

Examples of aminophenols include, but are not limited to, 3-aminophenol,5-amino-2-chlorophenol, 4-aminophenol, 3-amino-2-methylphenol,3-amino-4-methylphenol, 5-amino-1-naphthol, 6-amino-1-naphthol,8-amino-2-naphthol, 6-amino-2-naphthol and 4-amino-1-hydroxy-biphenyl,etc.

Other groups which may be included in the mesogenic repeat unit includeparaphenylene (—Ar—) wherein Ar represents an aromatic ring, as well assubstituted paraphenylenes such as para-diacetoxyphenylene(—CH₂COOCH2-Ar—CH₂COOCH₂—).

Any combination of such groups may also be incorporated into the repeatunit in the LC block of the LC block copolymer. For a discussion ofthese structural groups, see for example, U.S. Pat. Nos. 4,663,422 and5,017,304 and 5,030,703 for a discussion of such structural units, eachof which is incorporated by reference herein in its entirety. See alsoU.S. Pat. Nos. 4,238,599, 4,801,677, 5,173,562, each of which isincorporated by reference herein in its entirety, for further examplesof suitable mesogenic units.

Other suitable mesogenic repeat units include those of the followinggeneral formula:[-A-Y—X—Z—]_(m)wherein X can be (CH₂)_(n) wherein n is an integer from about 2 to about10, m can range from about 2 to about 50, Y and Z can each independentlybe —COO or —CONH or can be a single bond between two carbon atoms, and Acan be p-phenylene, 1,4-naphthylene, 2,6-naphthylene or 1,5-naphthylene,monosubstituted phenylene with methyl, chloro or phenyl substitution,—ArCH═CHAr— wherein AR is a phenyl ring, —Ar—COOAr—, —Ar—CONHAr—, or—Ar—OOC—Ar—COO-AR-, etc. For a discussion of such mesogenic repeatunits, see U.S. Pat. No. 4,952,334, the entire content of which isincorporated by reference herein.

Another specific example of a suitable aromatic mesogenic repeat unithas the structure —Ar—CO—NH—Ar—NH—CO—Ar—.

Other suitable mesogenic repeat units which can be employed herein aredescribed by Ober et al. in Polymer Journal, Vol. 14, No. 1, pp. 9-17(1972) and have the following structure:—[—OArCOO(CH₂)_(n)OCOArOCOArCO—]—_(x)wherein Ar represents phenyl with para-bond sites, n may range fromabout 2 to about 10, and x can range from about 2 to about 50. Thesemesogenic units can be characterized as aromatic ester mesogenic unitscomprising three linearly-aligned aromatic rings.

The type of mesogenic repeat unit represented by the formula above,wherein Ar represents phenyl with para-bond sites, n is an integer offrom about 2 to about 10, and x is an integer of from about 5 to about15, is described in U.S. Pat. No. 5,508,338, the entire content of whichis incorporated by reference herein.

Other specific examples of suitable mesogenic repeat units includepoly(hydroxynaphthoic acid) (—O—ArAr—CO—, wherein ArAr is two fusedbenzene rings) and poly(p-phenyleneterephthlate) (—O—Ar—OOC—Ar—CO—).

Another specific example of a suitable LC block employs a combination ofhydroxybenzoic and hydroxynaphthoic acid and has repeating units of theformula —[—O-AR-CO—]_(x)—[—O—ArAr—CO—]_(y)— wherein x and y are positivenumbers of 1 or more, for instance, x and y may vary independently fromabout 1 to about 50, and suitably about 1 to about 25. In someembodiments x=y=1 and in other embodiments x≠y. See, for example, U.S.Pat. Nos. 6,552,127, 6,054,537, 5,869,574, 5,767,198 and 5,750,626, eachof which is incorporated by reference herein in its entirety.

Another example of a mesogenic unit formed using a combination includesthat shown in U.S. Pat. No. 4,912,193, the entire content of which isincorporated by reference herein, employing a combination of p-hydroxybenzoic acid, 4,4′-dihydroxy diphenyl, terephthalic acid, andisophthalic acid.

The mesogenic repeat unit of the present application may be said toinclude both a mesogenic portion and a spacer. The mesogenic repeatunits of the A block can be attached together in such a way that themesogen portion of the mesogenic repeat unit forms a part of thebackbone (main chain liquid crystal polymer structure), or they may beattached together in such a way that the mesogen is attached to thepolymer backbone as a pendant group (side chain liquid polymerstructure). Examples of mesogenic repeat units employed in main chainliquid crystal polymers wherein the mesogen portion of the mesogenicrepeat unit forms a part of the backbone is hydroxynaphthoic acid, andpoly(p-phenyleneterephthalate).

An example of a mesogenic repeat unit resulting in a side chain liquidcrystal polymer structure has the following structure:

The A block or LC block of the liquid crystal block copolymer may bemade using any method known in the art. Most are made using conventionalcondensation reactions. See for example Chen, Bor-Kuan, et al.,“Synthesis and properties of liquid crystalline polymers with low Tm andbroad mesophase temperature ranges,” Polymer, 46 (2005) 8624-8633,Hurdoc, Nicolae, et al., “Thermal behaviour and molecular modeling ofsome aromatic polyethers containing a hexamethylenic spacer,” PolymerDegradation and Stability, 72 (2001) 441-445, Liu, Yingliang, et al.,“Synthesis and characterization of liquid crystalline copolyesterscontaining horizontal and lateral rods in main chain (II),” Reactive &Functional Polymers, 64 (2005) 35-46, Makaruk, Leszek, et al.,“Mesophase transitions in liquid crystal polymers”, Reactive &Functional Polymers, 33 (1997) 225-231, Gopalan, Padma, et al.,“Rod-Coil Block Copolymers: An Iterative Synthetic Approach via LivingFree-Radical Procedures,” Journal of Polymer Science: Part A: PolymerChemistry, Vol. 41, (2003) 3640-3656, Hakemi, H., “On the miscibility ofliquid crystalline polymers,” Polymer, 41 (2000) 6145-6150, each ofwhich is incorporated by reference herein in its entirety.

Whereas it is the A block of the liquid crystal block copolymer whichprovides the block copolymer with strength, stiffness and rigidity, theB block of the liquid crystal block copolymer is the soft segment of theblock copolymer and provides the polymer with flexibility. Suitably, theB block is aliphatic. Suitably, the B block has less than 10%aromaticity by weight of the B block, more suitably less than 5% byweight of the B block, and most suitably, the B block has substantiallyno aromaticity. Suitably, the B block is derived from repeating units ofolefins, esters, ethers, amides, and siloxanes, for example.

Examples of suitable repeating units for formation of the B blockinclude, but are not limited to, amides, esters, ethers, imides, olefinsand siloxanes.

In some embodiments, the B block is formed from hydrophilic monomerunits. Examples of suitably hydrophilic monomers include, but are notlimited to, short chain aliphatic ethers such as polyethylene oxideglycol or polytetramethylene oxide glycol which are the chain ends ofhydrophilic macromolecules, diols or dicarboxylic acids containing ametal sulfonate group, oligomers such as polyalkylene glycolcopolymerized with other monomers such as aliphatic dicarboxylic acids,hydrophilic acrylates available from Sartomer such as polyethyleneglycol diacrylate, acrylamides and N,N-dimethylacrylamide,N-vinylpyrrolidone, etc.

The above lists are intended for illustrative purposes only, and not asa limitation on the scope of the present invention.

The A block may have anywhere from about 2 to about 50 repeating units,and more suitably about 2 to about 25 repeating units, and the B blockmay have anywhere from about 2 to about 25 repeating units, and suitablyabout 2 to about 10 repeating units.

In embodiments wherein the block copolymer further has a C block, themesogenic units of the C block may be selected from those mesogenicrepeat units discussed as useful in forming the A block. However, in aliquid crystal polymer having both an A block and a C block, the C blockis formed from different mesogenic repeat units than those of the Ablock. For example, in one embodiment, the A block of the liquid crystalblock copolymer is a polyamide segment formed using and the C block is apolyester segment formed using aromatic hydroxycarboxylic acids, forexample. Examples of suitable mesogenic units for formation of thepolyamide A block structure include, for example,

This portion of the liquid crystal block copolymer can be made by thecondensation reaction between HOOC-AR-COOH (benzene-1,4-dicarboxylicacid) and H₂N-AR-NH₂(1,4-diaminobenzene) to form the followingstructure:

In this embodiment, suitable B blocks may be formed by condensation ofhexanedioic acid and hexamethylenediamine (nylon 6,6), ring openingpolymerization of caprolactam (nylon 6) or ring opening polymerizationof laurolactam (nylon 12), for example.

Nylon 6 (polycaprolactam) is not a condensation polymer, but rather isformed by the ring opening polymerization of caprolactam monomers.

Nylon 6,6, on the other hand, is formed by condensation betweenhexandioic acid (adipic acid) and 1,6-diaminohexane(hexamethylenediamine): repeating unit:H₂N(CH₂)₆NH₂+HOOC(CH₂)₄COOH→[—NH—(CH2)₆-NH—CO(CH2)₄-CO—]_(n)+H₂O

Hexanedioyl dichloride may be used in place of hexanedioic acid.

The liquid crystal polyester A block, the nylon B block and the liquidcrystal polyamide C block can be connected via conventional condensationreactions.

The C block may also have anywhere from about 2 to about 50 repeatingunits, and more suitably anywhere from about 2 to about 25 repeatingunits.

The above lists are intended for illustrative purposes only, and not asa limitation on the scope of the present invention.

Suitably, the A block is from about 50% to about 95% by weight of theblock copolymer and the B block is about 5% to about 50% by weight ofthe block copolymer, more suitably, the B block is about 10% to about30% by weight of the block copolymer. In some embodiments, the B blockor soft segment is about 10% or less by weight of the LC blockcopolymer.

Any suitable method of polymerization may be employed depending on themonomers, oligomers, or polymers which are employed. Most commonly, thepolymerization can be accomplished via condensation reactions which areachieved through reacting molecules incorporating alcohol, amine orcarboxylic acid (or other derivative) functional groups. An ether,amide, or ester linkage is formed and a small molecule, commonly water,is released. Thus, only a part of the monomer becomes part of thepolymer.

Addition polymerization, wherein the entire monomer becomes part of thepolymer, may also be employed. For example, anionic polymerization canbe used to prepare block copolymers. In such a process, a reactive siteremains at the end of the chain until it is quenched. The unquenchedpolymer may be referred to as a living polymer, and the addition of asecond monomer can result in a block polymer. These processes may beemployed where reactive unsaturated sites, i.e. double or triple bonds,are present. Most addition polymerizations are also chain growthpolymerizations wherein one monomer is added at a time, although thereare exceptions.

Example

In a specific example 4-hydroxy-2-benzoic acid (HBA) may be acetylizedto 4-acetoxybenzoic acid (ABA) with acetic anhydride as the solvent inthe presence of a catalytic amount of sodium acetate in the manner ofChen et al, “Synthesis and properties of liquid crystalline polymerswith low T_(m) and broad mesophase temperature ranges,” Polymer, 46(2005) 8624-8633. Still following the method of Chen et al, ABA then maybe reacted with 1,4-butanediol (BDO) in a molar ratio of about 1:3 andSb₂O₃ catalyst in an amount of about 300 ppm to produce the esterABA-BDO-ABA.

Polymerization is then accomplished by adding a mixture of the esterABA-TMG-ABA, terephthalic acid (TPA), a nylon 6 polymer terminated onboth ends with acid groups (Ny6) and 250-300 ppm of Sb₂O₃ or Ti(OBu)₄catalysts to a flask with a nitrogen purge using a molar ratio of theester to TPA to Ny6 dicarboxylic acid of 1.0:0.67:0.33. The nitrogenoutlet is equipped with a distillation column with vacuum. The mixtureis heated at melt for about 5 hours at a temperature of about 200° C. toabout 250° C., depending on the temperature necessary to melt themixture. Thermal stabilizers and antioxidants such as Irganox® 1010available from Ciba-Geigy are used added to inhibit decomposition. Themixture is stirred, for instance at 200 rpm once the melt temperaturehas been reached. The nitrogen flow is regulated to prevent evaporationof reactants. After about 3-5 hours the temperature is graduallyincreased to about 280° C. and the acetic acid produced by condensationis removed by distillation. When no more distillate is observed a vacuumof about 10 torr is applied for 2-3 hours and then the vacuum is reducedto 1-2 torr and the mixture stirred continuously for an additional 4hrs, all the while maintaining the temperature at about 280° C. Theproduct is then allowed to cool. Monomers and oligomers may be removedby Soxhlet extraction using acetone.

The resultant polymer is an A-B-A block copolymer having a structure of[(ABA-BDO-ABA-TPA)_(x)ABA-BDO-ABA]-Ny6-[ABA-BDO-ABA-(TPA-ABA-BDO-ABA)_(y)].

In modifications of the above equivalent amounts of ethylene glycol or1,3 propane diol may be substituted for 1,4-butanediol,6-hydroxy-2-naphthoic acid may be substituted for 4-hydroxy benzoicacid, 2,6-naphthalene dicarboxylic acid may be substituted for TPA,and/or other diacid terminated nylon polymers such as nylon 6,10 ornylon 9,12, may be substituted for the nylon 6 polymer. An A-B diblockcopolymer may be synthesized in a similar manner using a mono-acidterminated nylon polymer such as nylon 12, in place of the nylon 6diacid. Furthermore the relative ratio of short diacid to acidterminated nylon can be varied over a very wide range for instance fromabout 1:10 to about 1:10 on an acid equivalents basis.

The liquid crystal block copolymer of the invention may itself beemployed in the formation of medical devices or components thereof, or,the liquid crystal block copolymer may be blended with another polymeror polymers. In the latter case, suitably, the polymer and the B blockmay be selected so as to be compatible with one another. Compatibility,as used herein, refers to compatibility on both the macroscopic andmicroscopic, i.e. molecular, scale. Thus, compatibility on a macroscopicscale, may refer to those polymer blends which do not exhibit grossphase separation.

In polymer mixtures, the matrix polymer may interact strongly with theLC block copolymer or one block of the LC block copolymer, thusproviding desirable polymer properties.

In mixtures wherein the LC block copolymer is blended with otherpolymers, at least one other polymer of the blend, may be selected fromthose polymers which are non-liquid crystal polymers. Examples ofsuitable polymers which may be used for blending with the LC blockcopolymer described herein include, but are not limited to, polyestersand copolyesters, polyamides, polyethers, polyimides, polyolefins andsilicones, for example. These polymers are intended for illustrativepurposes only, and not as a limitation on the scope of the presentinvention.

Specific examples of suitable polymers which may be employed in a blendinclude polyamide elastomers such as those sold under the tradename ofPEBAX® available from Arkema, headquarters in Paris, France, andpolyester elastomers such as those sold under the name of HYTREL®available from DuPont in Dover, Del. are also suitable for use.

For example, if the liquid crystal block copolymer is blended with apoly(ether-block-amide) copolymer having an (AB)_(n) block copolymerstructure wherein the A block is nylon and the B block ispolytetramethylene oxide, a suitable LC block copolymer B block mayinclude amide repeat units or a polytetramethylene oxide structure. Theblock may suitably be less than about 50% by weight of the LC blockcopolymer, more suitably about 30% by weight or less of the LC blockcopolymer and most suitably about 10% by weight or less of the LC blockcopolymer.

The tensile strength of a typical poly(ether-block-amide) thermoplasticelastomer of the type described above has tensile strength of about10,000 psi and DSC melting point of about 174° C.

Suitably, the LC block copolymer, to act as a reinforcing material insuch a polymer blend, has a tensile strength of greater than about10,000 psi, for example, greater than about 12,000 psi, more suitablygreater than about 20,000 psi and most suitably greater than about30,000 psi.

Thus, it is desirable to select the LC block copolymer structure so thatit has a strong interaction with the thermoplastic elastomer to achievemechanical strength enhancement through effective load/forcetransferring.

It is also desirable that the LC block copolymer have a melting pointwithin a thermoplastic processing window of less than the thermaldegradation temperature of the thermoplastic elastomer. In the casewhere the thermoplastic elastomer is poly(ether-block-amide), forexample, the melting point range is suitably less than about 240° C.Extrusion/coextrusion is an example of a suitable method to process suchthermoplastic materials.

The above example is intended for illustrative purposes only, and not asa limitation on the scope of the invention. Other polymers are known tothose of skill in the art and may also be employed herein.

If a blend of polymers is employed, the amount of LC block copolymer issuitably about 75% or less and more suitably about 50% or less. Theamount of LC block copolymer employed may be from about 5% to about 75%and more suitably about 5% to about 50% and even more suitably about 10%to about 30%.

The at least one second polymer or blend of polymers may be employedfrom about 25% to about 95%, more suitably about 50% to about 95% andeven more suitably about 70% to about 90%.

The present compositions may be employed in the manufacture of anymedical device or component thereof which is suitably formed frompolymer compositions. Examples include catheter assemblies used indiagnosing and treating diseases such as vascular diseases.

The present invention finds utility in the manufacture of expandablemedical balloons, particularly those employed in the cardiovascularsystem wherein the balloon size is very small.

Balloon formation is known in the art. In some processes, a tube ofpolymer material is extruded and then expanded radially and axially.Balloon formation is described in U.S. Pat. No. 4,490,421 and incommonly assigned U.S. Pat. No. 6,024,722, both of which areincorporated by reference herein in their entirety. Of course, otherprocesses are known and may be employed in the present invention.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the attached claims. Thosefamiliar with the art may recognize other equivalents to the specificembodiments described herein which equivalents are also intended to beencompassed by the claims attached hereto.

1. A liquid crystal block copolymer, the liquid crystal block copolymercomprising: i. at least one A block, the A block comprises mesogenicrepeat units; and ii. at least one B block, the B block comprises nylon.2. The liquid crystal block copolymer of claim 1 wherein the B blockcomprises at least one member selected from the group consisting ofnylon 6,6, nylon 6 and nylon
 12. 3. The liquid crystal block copolymerof claim 1 wherein the A block comprises 4-acetoxybenzoic acid (ABA) and1,4-butanediol (BDO).
 4. The liquid crystal block copolymer of claim 1having the general structure[(ABA-BDO-ABA-TPA)_(x)ABA-BDO-ABA]-Ny6-[ABA-BDO-ABA-(TPA-ABA-BDO-ABA)_(y)].5. The liquid crystal block copolymer of claim 1 wherein the A blockcomprises mesogenic repeat units having the following general structure:


6. The liquid crystal block copolymer of claim 1 wherein said B blockcomprises 0% to about 10% aromaticity.
 7. The liquid crystal blockcopolymer of claim 1 wherein said A block comprises at least one memberselected from the group consisting of aromatic dicarboxylic acids,aromatic hydroxycarboxylic acids, aromatic amino carboxylic acids,diphenols and aminophenols.
 8. The liquid crystal block copolymer ofclaim 1 wherein said A block comprises at least one aromatic group perrepeat unit of said A block.
 9. The liquid crystal block copolymer ofclaim 1 wherein said A block comprises two aromatic groups per repeatunit of said A block.
 10. A composition comprising the liquid crystalblock copolymer of claim 1, the composition further comprising at leastone polymer selected from the group consisting of polyolefins,polyesters, polyethers, polyamides, polyimides, block copolymercomprising at least one polyolefin, polyester, polyether, polyamide orpolyimide segment, silicones and mixtures thereof.
 11. A compositioncomprising the liquid crystal block copolymer of claim 1, thecomposition further comprising poly(ether-block-amide).
 12. Thecomposition of claim 11 wherein said composition comprises about 5% toabout 30% of said liquid crystal block copolymer and about 70% to about95% of said poly(ether-block-amide).
 13. The liquid crystal blockcopolymer of claim 1 having a structure selected from the groupconsisting of A-B diblock, (A-B)_(n) wherein n is 3 to 20, B-(A-B)_(n)-Bwherein n is 3 to 20, A-B-A triblock, B-A-B triblock having softsegments at the free chain end, A-B-A-B-A pentablock, multiblockpolymers such as A-B-C or A-C-B triblock, B-(A-B-C)_(n)-B wherein n is 3to 20 and random block copolymers.
 14. The liquid crystal blockcopolymer of claim 13 having a structure selected from the groupconsisting of A-B-C, A-C-B triblock, B-(A-B-C)_(n)-B wherein n is 3 to20 and random block copolymers, the C block is a liquid crystal polymerblock derived from different mesogenic repeat units than the A block.15. A medical device wherein at least a portion thereof comprises theliquid crystal block copolymer of claim 1 and at least one non-liquidcrystal polymer.
 16. The medical device of claim 15, the medical deviceis a catheter assembly.
 17. The medical device of claim 15, said atleast a portion thereof is a catheter shaft.
 18. The medical device ofclaim 15, said medical device is an expandable medical balloon.
 19. Aliquid crystal block copolymer, the liquid crystal block copolymercomprising: i. at least one A block, the A block comprises mesogenicrepeat units; and ii. at least one B block, the B block comprises atleast one member selected from the group consisting of polyamides,polyesters, polyethers, polyimides, polyolefins and polysiloxanes. 20.The liquid crystal block copolymer of claim 19 wherein said B block isaliphatic.